Stretching–buoyancy interplay in the magma-poor rifting process

Abstract

Abstract The Cauvery Basin in East India represents a failed rift zone in the west and transform-related termination in the east. The deformation associated with a westward-propagating rift zone involves stretching and necking-related deformation from west to east. The rift axis and the flanks exhibit maximum and minimum deformation. In this study, we document the increasing role of buoyancy-driven processes and the development of the rift asymmetry during the advanced stages of rifting in a magma-poor setting. We use a series of reflection seismic profiles intersecting the failed rift zone maturing eastward. The onset of buoyancy-controlled extension correlates with the localized extension. It creates a relatively symmetrical axial dome, and exhibits rift flank rotations and central up-warping. This permanent uplift is associated with lower crustal ductile flow. Notably, the deep-seated syn-rift buoyancy forces progressively operate eastward. We deduce the associated transient dome uplift and its subsequent dissipation using a seismic flattening technique. The axial dome formation is associated with an upwelling asthenosphere and lower lithospheric mantle. This correlates with localized contraction within flat-lying fault blocks at its flanks, concurrently forming the typical hanging-wall and footwall geometry. The multiple shallow- to deep-seated mechanisms promote strain acceleration in the uplifted regions along the rift zone.